In your store you can have a lot of products but some of shop items /products may be needs only one or few specific payment gateway :

So using this plugin simply the shop admin can force the payment gateway for the single product by checking the desired payment gateway to be used in the product backend . some examples of products which need to have the forced payment gateway:

Products which can be paid only by Paypal and no other type of payment .

Products which can be paid only by Cash on Delivery and no other type of payment .

Products which can be paid only by Bank Transfer and no other type of payment .

Products which can be paid only by only by Any external payment gateway as:Ogone , NAB, Echeck , PaypalPro, Nochex , FirstData ,Paymill , Credit Cards and others and no other type of payment .

There can be a lot of examples in real life depending by the product that the online shop it is selling .